ISTANBUL (AP) — A U.S official has called for the trial of a Turkish employee of the U.S. Consulate on espionage charges to be resolved "swiftly, transparently and fairly."

The trial was adjourned Wednesday until June 28.

Metin Topuz, a translator and assistant for the U.S. Drug Enforcement Agency, has been jailed on charges of espionage and attempting to overthrow the Turkish government. His case is one of several issues that have strained ties between the NATO allies.

Topuz is accused of links to U.S.-based Turkish cleric Fethullah Gulen, who the Turkish government blames for the 2016 coup attempt. Topuz, who faces a life sentence if convicted, denies the charges.

U.S. charge d'affaires Jeffrey Hovenier told reporters there was "no credible evidence of any criminal wrongdoing" against Topuz.